1. Field of the Invention
The present invention relates generally to rotary kinetic fluid motors or pumps, and more specifically to stator vanes in a compressor of a small turbomachine and, in particular, to the damping of vibrations transmitted to such stator vanes from the casing of the turbomachine.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
A turbomachine, such as a compressor in a gas turbine engine, includes a plurality of stages of rotor blades to compress the air and a plurality of stages of guide vanes or nozzles that act to guide the airflow into the rotor blades. The compressor is subject to vibration stresses and fatigue from rotor imbalances and pressure differentials within the gas turbine engine, as well as from others. The vibrations can be so severe that the lifetime of the compressor or casing, or the rotor blades and stator vanes, can be damaged. Excessive wear or part damage can occur from rubbing between vibrating engine parts. These rubs are undesirable due to wear gaps, which can decrease engine performance, that are created between the rubbing parts. Therefore, because close tolerances between engine parts are required for good engine performance, minimization of engine vibration is desirable.
Vibrations are of greatest concern when the resonance frequency of the engine component part lies within the frequency range of the vibrations expected to occur during normal engine operations. Rotor blades and stator vanes are subject to nodal diameter vibration, a form of vibration characterized by two (or more in higher vibration modes) nodes on the circumference of the component part remaining stationary while parts there-between oscillate. In small turbomachine, the stator ring is typically cast as a single small piece. Because of the size, it is not economical to produce a multiple vane stator ring since the individual vanes could be as small as ½ inch in length.
It is an object of the present invention to reduce vibrations in a stator vane ring of a small turbomachine.